Background
Since the mid-1980’s, obesity has increased dramatically across developed countries [
1] with socioeconomically disadvantaged African American populations disproportionately affected [
2‐
4]. Physical activity is considered crucial for weight loss and maintenance, and it has many health benefits, including improved cardiometabolic disease risk profiles [
5‐
7], glucose metabolism [
5,
8], and better functional health in older adults [
9]. Indeed, the Physical Activity Guidelines recommend that adults do at least 150 min a week of moderate-intensity, or 75 min per week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity in order to achieve substantial health benefits [
10]. Yet most Americans fall far short of achieving the recommended levels of physical activity and the groups of people with the highest rates of obesity, low-income, racial/ethnic minority women, and the elderly, are also the groups least like to achieve recommended levels of activity [
11,
12].
Increasingly, policy efforts have focused on modifying neighborhoods with the goal of promoting physical activity. On one hand, structural characteristics of neighborhoods, including greenspaces and aesthetically pleasing environments such as tree-lined streets and parks, and high rates of walkability (i.e., environments that promote walking through sidewalks, traffic calming measures, etc.) may encourage physical activity and reduce obesity [
13‐
16]. On the other hand, people living in socioeconomically deprived areas with high crime rates may worry about safety and limit their activity outdoors in spite of potentially high walkability or even greenspace [
17‐
19] Therefore, policy makers need to understand which strategies may improve MVPA for people living in socioeconomically disadvantaged neighborhood where safety concerns may hinder physical activity [
20,
21].
Still, neighborhood environments are complex and the role of objectively measured crime, combined with neighborhood walkability (e.g., pedestrian safety and mixed land use), and the concurrent role of these factors in influencing physical activity behaviors are not well understood (see reviews [
22,
23]), especially in low-income African American populations [
24,
25]. The overarching assumption is that increasing opportunities for physical activity in a neighborhood, both in terms of the structural characteristics and safety of the environment, will motivate residents to take advantage of the new opportunities and thereby increase their activity. However, increasing evidence (albeit mixed) suggests that associations between crime and neighborhood greenspace and walkability on physical activity differ according to age and sex, especially at older ages [
17,
26‐
29] when physical activity declines [
11,
30,
31]. For instance, among Canadian adults (mean age 41 years), women were more likely than men to feel unsafe, limit their walking and perceive less neighborhood walkability [
27]. However, this study was based on a Canadian sample of relatively high-income (~60% with income > $60,000) white people that limits generalizability. In the U.S., a 7-year study of a large cohort of young ethnically diverse US adults (ages 11 to 29 years) showed that associations between self-reported frequent bouts of MVPA with objectively measured landscape diversity and lower crime rates are consistent in males and females [
19]. In an older, more socioeconomically disadvantaged sample of 901 adults (mean age 45 years) living in 55 low-income District of Columbia neighborhoods, that included objective measures of crime and walkability, women were more likely than men to report less walking because of fear, but gender differences in fear between men and women shrank as neighborhood violence increased [
29]. In one of the few studies that examined predictors of accelerometer-derived MVPA in older adults across multiple countries, perceived safety from crime, and lack of barriers to walking were positively associated with MVPA but only in older adults (>55 years) [
17]. In sum, much of the evidence is limited by self-reported activity that is vulnerable to bias [
11] and a dearth of literature that examines objectively measured environmental attributes and relationships in older low-income African Americans who are at greatest risk of low rates of MVPA [
11,
12] and inactivity related diseases, such as obesity [
32‐
34].
This cross-sectional study capitalizes on a cohort of predominantly African American, low-income residents living in two urban Pittsburgh neighborhoods, the Hill District and Homewood. The Hill District is predominantly African American with 45% of African American residents earning an income below the federal poverty line (U.S. Census Bureau). Nearly 20% of the Hill’s residents in the civilian labor force are unemployed (with many others under-employed) (U.S. Census Bureau), and 35.8% report no access to a vehicle. The population Homewood population is 90–97% African American and is comparable sociodemographically to the Hill District [
35]. We examined the association between objective measures of the built and social environment and individual-level physical activity measured with accelerometers. We tested associations between neighborhood greenspace, walkability (e.g., pedestrian safety and mixed land use), crime and MVPA. We further examined whether these relationships were modified by age and sex. Consistent with prior literature, we hypothesized that neighborhood crime would play a stronger role on MVPA for women than for men [
17,
27,
36] and that neighborhood walkability and greenspace would impact MVPA more so in younger than in older adults [
11,
37].
Discussion
This urban low-income and predominantly African American study population engaged in almost no MVPA. On average they engaged in about 6 min of MVPA per day or 42 min per week which is less than one third of the recommended levels of moderate intensity activity [
10]. MVPA was even lower among women versus men and among those aged 65+ versus < 65 years. Lower rates of MVPA in older populations and women are consistent with findings from various countries where midlife and older adults accumulate 4–41 min of MVPA per day [
30,
57‐
59]. Among a large sample of white and black adults (ages 49–99 years) living in the U.S. white and black women accumulated merely 3–4 min/day of MVPA [
59]. One reason we observed such low MVPA rates in our population may be due to poor health that limits activity. On average, about 30% of our population reported that a physical limitation prevented them from walking one block. Even among the younger men who were about 46 years old, about 1 in 5 reported being physically limited. Interventions are critical to promote physical activity in underserved minority populations who have little time and resources, who are far less active than more advantaged populations [
60‐
63], and who are burdened with more health limitations.
While policy efforts increasingly aim at community-level interventions to improve MVPA in disadvantaged neighborhoods, we found little evidence that the built and social environment impacted MVPA in this older adult, low income and predominantly African American cohort. Neither greenspace nor crime was associated with MVPA overall or in sex and age subgroups. The neighborhoods we studied had very little greenspace (approximately 3%), and that could have contributed to null findings. Compared to another study among New Zealand deprived neighborhoods that evaluated the proportion of usable greenspace in relation to obesity greenspace ranged only from 1 to 5% [
64]. In addition to living near little greenspace, residents living in the Hill District and Homewood were also exposed to high crime rates. Based on Pittsburgh police data, the Hill District and Homewood typically have higher rates of violent crime, property crimes, and rape than other Pittsburgh neighborhoods [
65]. The lack of associations we present here adds to the mixed literature. Despite researchers’ increased attention to the effects of neighborhood greenspace and crime on MVPA, findings were inconsistent and mixed across studies even when authors accounted for age and sex interactions [
18,
28,
29,
66,
67]. However, ours was one of the few studies to examine objectively measured neighborhood walkability, greenspace, crime, and physical activity [
68].
Consistent with our hypothesis, we observed a significant interaction between age, sex, and walkability, such that women aged <65 years living in walkable neighborhoods engaged in more MVPA than their older counterparts. While these results are encouraging, the effects appeared to be modest, such that the predicted amount of time spent in MVPA increased from 2 to 6 min/day in the most walkable surrounds among women < 65 years. The small effect may be due to poor walkability in these neighborhoods, with an average walkability index of 8 (max = 12) compared to the possible range of 0 to 22. However, our findings are comparable to the average walkability index of 6 that was reported in a national sample of public secondary school students and their communities [
49]. The 4 min/day increase in MVPA (based on the difference in predicted 2 to 6 min of MVPA/day in Fig.
2) translates to a medium effect size of 0.3 (mean difference of 4 divided by standard deviation 12) [
69] but increasing MVPA in sedentary adults is difficult. By comparison, an intensive 5-week intervention delivered face-to-face for 45 min for 18 inactive university employees randomly assigned to an intervention group to achieve 10,000 steps increased their daily MVPA from 20 to 35 min, an effect size of 1.1 [
70]. While small changes in environment (often also more cost-effective relative to individual-level interventions) [
71] may have a moderate effect on an individual they can have a significant population-level impact.
When examining neighborhood effects on health and health-related behaviors, important relationships could be missed when interactions are ignored and analyses pool across heterogeneous groups of people. For example, in a prior study, park proximity significantly interacted with retirement status such that non-retired participants who reported living near a park were more likely to participate in recreational walking, whereas no relationship was observed in retired participants [
72].
We present data from a unique low-income and predominantly African American cohort living in underserved urban neighborhoods that includes a variety of detailed environmental data combined with individual-level characteristics and objectively measured MVPA. Accelerometry is superior to self-report where over-reporting can bias estimates [
11]. Further, our study population are known to be at increased risk of residing in disadvantaged neighborhoods [
73,
74], limited physical activity [
11,
12] and suffering higher rates of inactivity-related cardiometabolic conditions [
32‐
34]. To our knowledge, this is the first analysis linking objective measures of greenspace, walkability, and crime to accelerometry-derived activity in an older, disadvantaged, and predominantly African American population. Yet our study has some limitations. First, small sample sizes across age and sex subgroups may have limited our ability to detect associations between the neighborhood and MVPA, and with 3-way interactions by age and sex. Next, this study is cross-sectional and thus does not capture changes in the environment or MVPA. In addition, our 1 km network neighborhood buffer may not accurately reflect physical activity areas for different urban settings and sociodemographic subgroups. Indeed other walkability indices using geographic information systems data exist and are based on density, diversity, and design [
75], such as the walkscore [
76] that may capture a larger geographic area surrounding the participants’ homes. However, the quality of these measures depends on the accuracy of the data and they often include only limited snapshots in time that may not coincide with the study period. In contrast, a street audit is limited by a smaller sample than when using GIS but can collect more detailed information about street quality (e.g., lighting and sidewalk condition). We opted to collect street audit that coincided with the participants MVPA survey and MVPA data collection and provided a unique set of very detailed data that was collected through labor-intensive street audit. Further, participants excluded from this analysis were younger which may have biased our results. Residential location choice is complex and driven by more than physical activity preferences. Yet, individual physical activity may be tied to unobserved characteristics (e.g., health consciousness) that underlie an individual’s residential location. Thus residential selection could bias our results.
Despite these limitations, our study is an essential step in understanding how living in deprived neighborhoods with few greenspaces, low walkability and high crime rates may influence MVPA differentially across an older population of African American adults. Our findings are significant in light of the recent efforts to improve physical activity through policies targeting the built environment. Indeed, the campaign ‘Step It Up! The Surgeon General’s Call to Action to Promote Walking and Walkable Communities’ [
77] recognizes that improving walkability through community design, transportation and land use is an important strategy to support American’s physical activity.
The need to improve low-resource neighborhoods is clear. In a large study including 7139 census tracts, comprising 9.5% of the 2010 US population, the availability of parks and recreational facilities was lower in predominantly minority census tracts relative to non-Hispanic white census tracts. [
78] However, it may take more than small changes in the built environment to increase MVPA. The social component of choosing to use one’s neighborhood for MVPA needs to be considered. For example, social cohesion is a potent factor that influences people’s choices to use their neighborhood public space for physical activity [
79]. Indeed, a community-level intervention aimed at improving the built environment in conjunction with a socially targeted program (e.g., family involvement) was more successful increasing physical activity in low-income neighborhoods than infrastructure interventions without a social component [
80]. Greater understanding of how lifestyle factors and neighborhood greenspace, walkability and crime interact to influence MVPA is needed to inform effective policy.
Acknowledgments
The authors express sincere appreciation and gratitude to La’Vette Wagner, field coordinator of the Pittsburgh Hill/Homewood Research on Eating, Shopping, and Health study and the data collection staff. The authors thank the Hill House Association, Operation Better Block, and Homewood Children’s Village. Without their participation, the study could not have happened.